A TOP-BLOWN REFINING METHOD IN CONVERTER FEATURING EXCELLENT DECARBURIZATION AND TOP-BLOWN LANCE FOR CONVERTER

摘要

A refining method for decarburization by blowing by using a top-blown lance having a gas-supplying pipe of at least one independent line, wherein the absolute secondary pressure Po of nozzle of the lance of at least one line is maintained to be not smaller than 0.7 times but not larger than 2.5 times of the properly expanding absolute secondary pressure Pop of nozzle of the lance, and the oxygen supplying rate is so changed that a maximum value of the absolute secondary pressure of the nozzle is not smaller than 1.1 times of a minimum value thereof. The top-blown lance used here has not less than 2 but not more than 10 shielding portions arranged in the openings at the end of the lance in a concentric polygonal shape or a concentric circular shape in cross section, has a ratio B/h of the length h (mm) of the short side to the length B (mm) of the long side of the openings separated by the shielding portions of from 10 to 225, has slit-like nozzles of which the ratio (B~h)/R is from 0.4 to 4 mm when the diameter of the lance is R (mm), and has 1 to 6 circular nozzles that are coupled to a gas-supplying pipe independent from said slit-like nozzles and are arranged on the inside of said concentric polygon or said concentric circle.